The present patent application is related to our copending patent application document “Method of Polymer Nanolithography”, AFD 654, Ser. No. 10/817,406 filed on Mar. 25, 2004. The contents of that application are hereby incorporated by reference herein.
The present invention relates generally to nanolithography and specifically to a polymer electrostatic nanolithography method based upon amplitude modulated Atomic Force Microscopy.
The use of nano and micro-scale structuring of polymers, whether as a sacrificial, pattern-transfer layer or as the active component in a nano-device, is integral to nearly every aspect of future material fabrication. Two general areas of interest are polymer patterning for micro/nanofabrication and ultra dense data storage. It is known that a fundamental limitation for the density of magnetic storage media such as computer floppy disks and the like is the so-called superparamagnetic limit that is related to spin—spin interactions. Ultra compact data storage in thin polymer films is a promising alternative to ferromagnetic storage mediums because polymer data storage overcomes this fundamental limitation, enabling ultra dense storage.
Recent nanolithography investigations are based on the spatially selective removal or deposition of polymer. While somewhat successful, the prior art techniques are generally slow to perform. These techniques generally require chemical cross-linking, and/or substantial polymer degradation or ablation to effect. This permanently changes the composition and structure of the media itself, rendering it ineffective for repetitive data storage and retrieval applications.
A recent polymer nanolithography technique is described in U.S. Pat. No. 6,249,747 to Binning et al. The Binning device utilizes a cantilevered tip within an Atomic Force Microscope wherein an electrically conductive material is attached to the cantilever. In use, an electric current is applied to the electrically conductive material in the cantilever, heating the cantilever and the tip, in turn. The tip, thus heated, is selectively applied to a heat deformable film to create pits. The pits are utilized to convey information by the creation of a coherent structure. While this technique is somewhat effective, it has the disadvantage that a specialized tip is required and the application of current to heat the tip slows the overall lithographic process because the cantilever is large, requiring additional time to cool down.
A need exists therefore for a high speed polymer nanolithography method that facilitates rapid polymer feature creation without polymer degradation, cross-linking or removal. Such a method would enable reliable, high speed feature creation, and additionally provide for a ready erasure process and subsequent re-patterning of the polymer film.